OBJECTIVES: Immunosuppressor factor produced by spleen cells and found in the circulation: A primary goal will be to isolate and determine the chemical nature and biological significance of the suppressor factor recovered from spleen cells of tumor bearing animals. Since the sera of tumor bearing mice shows a similar suppressor capacity, attempts will be made to demonstrate whether this is due to the same or some other material. The cell type responsible for production of suppressor factor has been identified as a nonadherent cell and will be further identified as a T-cell or B-cell, etc. Concentrated inhibitory factor will be tested in tumor bearing animals for its effect on tumor growth and on other immune parameters. Conversely splenectomy and inhibition of inhibitory factor with xenogeneic antibody will be used to counteract this effect in the intact tumor bearing animal. We have on hand serum from a large number of colon carcinoma patients and age-matched controls. These sera will be compared for nonspecific suppression of lymphocyte stimulation. b. Immune function of specific lymphoid cell populations in malignancy: It is now possible to produce relatively pure populations of a variety of lymphoid cells, including macrophages, B-cells and subclasses of T-cells, from normal or tumor immune animals. These will be tested primarily in vivo for their capacity to inhibit tumor growth by neutralization (the Winn test) or to abort the growth of establishd tumors. BIBLIOGRAPHIC REFERENCES: Subramanian, C., Yu, S. and McKhann, C.F.: Soluble suppression factor from the spleens of tumor bearing mice. FASEB (Abstract, 1977). Yu, S., Subramanian, C., Burk, M. and McKhann, C.F.: Cellular reactions in lymph nodes and spleens of tumor bearing mice. American Assocation for Cancer Research (Abstract, 1977).